[Effect of intravesical instillation of the antitumor chemotherapeutic agents mitomycin C and cytosine arabinoside on rat bladder carcinogenesis initiated by N-butyl-N-(4-hydroxybutyl) nitrosamine].

The effects of intravesical instillation of cytosine arabinoside (CA), mitomycin C (MMC) and combination of CA and MMC were examined in rats pretreated with N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN). Rats were given initial treatment with BBN for 4 weeks followed by intravesical instillation of drugs once a week for 12 weeks. The total observation period was 36 weeks. Instillation of MMC markedly increased the development of bladder tumors, although CA did not. Moreover, tumor incidence in the combination group was less than that with MMC only. The results indicate that the intravesical instillation of MMC promotes 2-stage bladder carcinogenesis, whereas CA does not. Moreover, it is suggested that CA inhibits the promoting effect of MMC.